Analog sources: Simon Yorke, Kuzma Stabi S, turntables; Graham 2.0, Immedia RPM2, Rega RB600 tonearms; Crown Jewel SE, EMT TU, Lyra Parnassus D.C.t, Grado Statement phono cartridges.
Preamplification: Ayre K-1; Audio Research Reference and Musical Fidelity X-LP2 phono sections.
Power amplifiers: Mark Levinson No.335, Ayre V-1.
Loudspeakers: Audio Physic Virgo, Sonus Faber Amati Homage.
Cables: Yamamura Millennium 6000, Cardas Golden Reference, Electra-Glide interconnects; Yamamura Millennium 6000 speaker cables; Yamamura Quantum, Electra-Glide…
search
Sidebar 2: Associated Equipment
Sidebar 3: Measurements
The KR Enterprise VT8000 was warmed up for one hour at a third of its rated maximum power. For an amplifier with a tube output stage, it runs relatively cool.
The VT8000's input impedance measured 62.6k ohms. Its measured minimum output impedance is 4.8 ohms at 20Hz; the maximum measured value is 6.6 ohms at 20kHz; and there was some dependence on the exact figure and the load impedance used to make this measurement. This amplifier's frequency response will be very dependent on the loudspeaker with which it is used. Voltage gain into 8 ohms was 26.8dB in…
Sidebar 4: Specifications
Description: Hybrid monoblock power amplifier with solid-state input and driver stages, and "vacuum transducer" output stage. Maximum power: 75W RMS (18.75dBW) into 4–8 ohms. Frequency response: 15Hz–35kHz, –3dB; 30Hz–20kHz, –0.5dB. Input sensitivity: switchable 350mV, 1V, 2V, 5V. Input impedance: 100k ohms.
Dimensions: 13.75" W by 10" H by 19.75" D. Weight: 92 lbs.
Serial numbers of units reviewed: 150R, 150L.
Price: $25,000/pair (1999); no longer available (2008). Approximate number of dealers: 5. Warranty: 3 years, parts & labor.
Manufacturer…
Manufacturer's Comments
Editor: First of all, I would like to take this opportunity to thank Stereophile for permitting Mr. Michael Fremer to review our "top-of-the-line" monoblock amplifier, the VT8000 MK, and to visit our factory in Prague, Czech Republic.
Second, if I may, I would like to respond to a number of inexplicable points that have been raised by your test-bench results that may give erroneous ideas of our sound quality and design philosophy, despite Mr. Fremer's very enthusiastic audition.
My primary duty is to answer, point by point, the results of the curves…
Michael Fremer returned to the VT8000 in December 1999 (Vol.22 No.12):
I've been reviewing audio gear for 13 years now, and never, never has the discrepancy between what I heard and what was measured been so great as it was with the KR Enterprise VT8000 MK monoblocks (Stereophile, November 1999). I didn't see the amps' disappointing measurements until the final review was faxed to me for fact-checking. I almost went into toxic shock. I am much more used to having John Atkinson or Tom Norton confirm what I heard; eg, the Audio Physic Virgo review, my first for Stereophile (September 1995…
More Manufacturer's Comments
Editor: I am taking up my pen again to respond...to Mr. Fremer's...additional commentary in his "Analog Corner" feature, where he says, "I was extremely disappointed and surprised to read the discrepancy between the KR's claimed power (75W) and measured power (40W and lower, depending on load impedance and distortion)." From this statement, it is evident from Stereophile's technical testing, [that] we are still in the horse-and-buggy age. Those may have ran very well on plowed fields, but if there is a Ferrari, it certainly cannot give the same performance.…
At the end of August, we watched as the number of registered users in our online forums quickly ticked past the 10,000 mark. Ten thousand registered users! While it might prove interesting to learn just how that number breaks down into men and women, old and young, subjectivists and objectivists, or any of several other demographic and philosophical divides, that would only obscure the point: In our online forums, there are over 10,000 members who are eager to share their enthusiasm for music and hi-fi. What a beautiful thing!
Among the 10,000, there will doubtlessly be some who have…
I can't think of a product that was as eagerly anticipated as was Ayre's KX-R preamplifier ($18,500). Following in the footsteps of Ayre's MX-R monoblock amplifier, a Stereophile 2007 Product of the Year, and milled, like the MX-R, from a 75-lb billet of aluminum, the KX-R also shares with its monoblock stablemate the Ayre ethos of zero feedback and fully balanced operation. But what really caused the buzz was the declaration by Ayre founder and chief designer Charles Hansen that the KX-R, with its use of a technology he calls Variable Gain Transconductance (VGT) to control the volume, would…
Also, since the signal is not attenuated before entering the active circuitry, source components with extremely high outputs could have been problematic. "We had to do a fair amount of work to ameliorate this potential problem," Hansen said. "With a typical source of 2V to 4V balanced output, the distortion is around 0.001% to 0.002%. Increasing the input to 8V RMS, as some digital products produce, will bring the distortion up to around 0.008% to 0.01%."
Hansen chose to set the input impedance at a high 1M ohm per phase (2M ohms balanced). "You know how, when you load a moving-coil…
I'll start with something that sounds simple: The KX-R was really quiet. (If this were a movie, somebody would have to say, "Yeah. Too quiet.") Aren't all audio components these days? Well, sure, but the KX-R, with an activated input selected and set to regular listening volume, was far more silent than the tomb. As Hansen said about the air, you don't notice it till it's gone.
Music sounded especially alive through the KX-R. I noticed this as much with the MF Nu-Vista 300 as I did with the MX-Rs. Want jump factor? The KX-R had it. John Atkinson kindly hand-delivered a CD-R containing…